Sampling particles from a gas stream presents several challenges. Traditional sampling methods are ill suited to the collection of vapor phase ultrafine particles. Many powders possess properties that lead to agglomeration and clogging in small features and narrow apertures. Due to their small size, ultrafine powders with effective diameters below 100 nanometers are subject to being acted upon by of even the slightest intermolecular forces. This generally such powders very difficult to handle and convey, and gives them a strong tendency to agglomerate with one another, and to adhere to surfaces and to small dimensions within mechanical devices.
These challenges must be confronted in the design of devices for sampling fine powders.